Background: For reasons of cost and ethical concerns, models of neurodegenerative disorders such as
Huntington disease (HD) are currently being developed in farm animals, as an alternative to non-human
primates. Developing reliable methods of testing cognitive function is essential to determining the usefulness
of such models. Nevertheless, cognitive testing of farm animal species presents a unique set of
challenges. The primary aims of this study were to develop and validate a mobile operant system suitable
for high throughput cognitive testing of sheep.
New method: We designed a semi-automated testing system with the capability of presenting stimuli
(visual, auditory) and reward at six spatial locations. Fourteen normal sheep were used to validate the system
using a two-choice visual discrimination task. Four stages of training devised to acclimatise animals
to the system are also presented.
Results: All sheep progressed rapidly through the training stages, over eight sessions. All sheep learned
the 2CVDT and performed at least one reversal stage. The mean number of trials the sheep took to reach
criterion in the first acquisition learning was 13.9 ± 1.5 and for the reversal learning was 19.1 ± 1.8.
Comparison with existing method(s): This is the first mobile semi-automated operant system developed
for testing cognitive function in sheep.
Conclusions: We have designed and validated an automated operant behavioural testing system suitable
for high throughput cognitive testing in sheep and other medium-sized quadrupeds, such as pigs and
dogs. Sheep performance in the two-choice visual discrimination task was very similar to that reported
for non-human primates and strongly supports the use of farm animals as pre-clinical models for the
study of neurodegenerative diseases.